The invention is directed to a process for the production of methyl isocyanate by reaction of an alkali cyanate with dimethyl sulfate.
It is known to produce methyl isocyanate through the action of alkali cyanates on methyl halides. The reaction takes place with methyl chloride, methyl bromide or methyl iodide in the presence of dimethyl formamide or N-methyl pyrrolidone and in the presence of a nitrogen compound, such as pyridine and a hydroxy compound such as phenol (Japan published application No. 089090) or with methyl chloride in the presence of dimethyl formamide under super atmospheric pressure (Japanese OS No. 089810). A disadvantage in this process is that either long reaction times are required or superatmospheric pressure is necessary.
It is also known to form methyl isocyanate in the thermal decomposition of methylcarbamic acid chloride in inert organic solvents. (Urbach, U.S. Pat. No. 3,969,389). Relatively good yields are produced but long reaction times are required so that the space-time-yield is small. Besides this process presupposes the production of methylcarbamic acid chloride by the reaction of phosgene on methylamine hydrochloride so that the process all together is expensive.
Finally it is known to produce methyl isocyanate by the action of dimethyl sulfate on potassium cyanates. The reaction is carried out in the presence of inert materials, especially in the presence of anhydrous sodium carbonate. The yield is merely 50 to 55% (Slotta, Berichte Vol. 58 (1925) pages 1320-1323).